Photographic objective having an iris diaphragm



w. MERT 2,015,491

PHOTOGRAPHIC OBJECTIVE HAVING AN IRIS DIAPHRAGM Sept. 24, 1935.

Filed March 15, 1934 V. .lo

c C S vvvvvvvvVvvvVV vvvvvvvvv Patented Sept. 24, 1935 ETE@ STI'TES param PHOTOGRAPHIC BJECTWE HAVING AN IRIS DIAPHRAGM f Willy Mert, Ilena, Germany, assigner to the firm Carl Zeiss, Xena, Germany 1 Claim.

I have filed an application in Germany, March When photographic objectives, especially wideangle objectives or objectives of great ratios of 5 aperture, are shut down, the image projected on the focusing screen or the light-sensitive layer by the entire objective is imaged with a comparatively small aperture, contrary to which the image of the diaphragm aperture is comparatively great. l Although, as a rule, the diaphragm aperture is not imaged in the plane of the focusing screen, shutting down the objective very much may entail that bright spots, so-called diaphragm spots,

appear in the middle of the image on the focusing"A 15 screen, these spots being sometimes rather inconvenient.

According to the invention, the said disturbingg spots are neutralized to a large extent by departing from the usual practice of having the edge 20 of the aperture always lie in one plane and provviding that different apertures correspond to different planes of this edge, the plane of this edge being for instance very near a lens surface next to the diaphragm when this diaphragm is closed 25 completely. The said improvement is realized by using an iris diaphragm in which the annular surfaces supporting the lamin of the diaphragm are inclined relatively to the optical axis of the objective, so that these lamin are displaceable 30 on a convex, for instance a spherical, surface. The consequent differences of the'positions of the diaphragm aperture also have a favourable influence upon the image errors and the like that depend on the ratio of aperture.

In the accompanying drawing, which illustrates the invention, Figure 1 represents in part-sectional elevation an objective containing an iris diaphragm, and Figure 2 shows in part-sectional elevation part of this objective, the iris diaphragm of the objective having in Figure 2 an aperture which is larger than the one according to Figure l. The diaphragm is disposed between two lenses a and b. The lamin c of the diaphragm are at- 5 tached to two conical surfaces d and e of annular bodies d1 and e1, the lamina: in the body dl being rotatable aboutA axes f and those in the body el having bolts g displaceable. in a groove g1. The body el is rotatable about the axis X-X of the objective. In this construction, the lamin represent, together, an approximately spherical surface. When adjusted according to Figures 1 and 2, the lamin provide apertures h and i, respectively. When the objective is stopped down very much (Figure 1), the aperture of the diaphragm lies nearer the interior surface of the lens b than it does when the diaphragm is widely open (Figl`ure 2).

` Iclaim': 20 In a photographic objective an iris diaphragm, this diaphragm containing a plurality of lamin and two annular bo ies which are concentric to the optical axis of the objective and next to each other in the direction of this axis, at least one of thes` Kbodies being rotatable about the said axis, those urfaces of the two bodies which face each other being inclined relatively to the optical axis of the objective, one end of each lamina being attached to the inclined surface of one body and the other end of each lamina being attached to the inclined surface of the-other body, so that rotations of the said bodies relatively to each other not only vary the aperture ot the diaphragm but also displace in the direction of the optical axis the plane of the diaphragm aperture, which is at Aright angles to said axis.

, WILLY MERT. 

